Home, office and other building-security systems are often used for safeguarding valuable possessions and for personal protection. These systems are typically implemented using different monitoring devices, such as cameras, motion sensors, keypads or contact sensors. Many buildings have multiple locations that are monitored for security purposes, requiring multiple monitoring devices in the different locations. For increased security and functionality, the monitoring devices can be configured to communicate with one or more central control devices. The central control device can, among other things, perform monitoring or recording functions, determine whether the building-security has been breached and whether to contact security personnel.
One method of communicating between the monitoring devices and the central control device is by a physical connection, such as electrical or other wiring. Using wiring to establish communication between the security devices can be troublesome for a number of reasons, such as the high cost of installation and maintenance. For example, exposed wiring is often unacceptable in a building, and thus, the installation of the security system requires passing the wires through the walls of the building. This type of installation can significantly increase the time required to complete a security system installation. Moreover, the troubleshooting and repair of the security system can be difficult because there is limited access to the unexposed wiring. The cost of the wire is another factor, especially in large buildings requiring numerous monitoring devices.
One potential solution is to use wireless monitoring devices to reduce or eliminate the need for physical connections between the devices, however, wireless security systems also have a set of problems, such as battery life. Ideally, the security devices would be self-powered by, for example, a battery. Self-powered devices are more secure because they are not subject to failure upon loss of power to the building. They also require less installation problems because they do not need to be connected to a separate power source; however, self-powered devices often have reliability issues due to the finite life of their power source. Increasing the useable time of a power source reduces the cost for replacement of the power source and increases the security of the entire system by having less potential downtime of the system or its components. Several recent developments have increased the potential power requirements of wireless security devices.
For example, the use of wireless communications in home, office and other buildings has been steadily increasing, creating additional issues with wireless security systems. One such issue is the increased potential for corrupted data due to interference between different wireless communications devices. This issue may also be present when an unauthorized person attempts to disrupt the security system by “jamming” the wireless communications using a wireless interference device. Techniques exist for reducing unwanted interference, however, the implementation of some of the techniques result in increased power requirements. Two such techniques, both of which can result in increased power requirements, include increasing the power of the transmission or varying the frequency of the transmission.
Another problem with power requirements arises from the desire to have increased monitoring capabilities with smaller devices. As security systems become more advanced, the power requirements of the monitoring devices are often increased. For instance, monitoring devices that contain digital cameras require enough power to run the camera, to store the digital picture in memory and to transmit the digital picture to the control device. The increased functionality of the monitoring devices, along with the desire to have smaller, less noticeable devices with less room for batteries or other power sources, has impacted the reliability of the monitoring devices.
Implementing a wireless building-security system can be further complicated by industry or government regulations. One such set of regulations is imposed by the Federal Communications Commission (FCC). The current regulations cover numerous aspects of wireless communications systems including, but not limited to, a range of restricted frequencies, a minimum number of different hopping frequencies within the allowable frequencies, the maximum output power of a transmitter and a requirement related to equal use of the hopping frequencies.
Attempts have been made to implement wireless security systems using a variety of methods. One such method is taught by European Patent No. EP 1 363 260 filed on May 6, 2003, entitled “Procédé de communication radiofréquence entre plusieurs dispositifs et système de surveillance mettant en oeuvre un tel procédé,” which is fully incorporated herein by reference. Yet, these methods still leave room for improvement.
These and other issues have presented challenges to the implementation of wireless communication devices, including those involving building-security systems and similar applications.